Journal of Applied Physiology, Vol 50, Issue 2 444-449, Copyright © 1981 by American Physiological Society
Efficiency of trained subjects differing in maximal oxygen uptake and type of training
M. K. Stuart, E. T. Howley, L. B. Gladden and R. H. Cox
This study was undertaken to examine the relationship between energy
expenditure and work rate on a bicycle ergometer in five sprinters and five
distance runners who differed in maximal oxygen uptake (VO2max) and type of
training. Each subject performed at work rates of 30, 60, 90, 120, and 150
watts (W). The relationship between energy expenditure and work rates was
most accurately described by a quadratic curve for both groups: for
sprinters, energy expenditure (kJ) = 11.57 + 0.1812 (W) + 0.00046 (W)2; for
distance runners, energy expenditure (kJ) = 11.74 + 0.1386 (W) + 0.00060
(W)2. Delta efficiency (delta work accomplished divided by delta energy
expended X 100%) decreased as work rate increased. Statistical analyses
revealed no significant differences between groups in delta efficiency at
the same work rate (P greater than 0.25) or at the same relative work rate
(P greater than 0.75). These results suggest that differences in VO2max
and/or type of training have little or no causal effect on the decrease in
delta efficiency with increasing work rate. The observed decrease in delta
efficiency may be due to increases in metabolism not directly related to
the performance of the external work or to an increasing amount of
unmeasured work as work rate increases on a bicycle ergometer.
